Money was established for exchange, but interest causes it to be reproduced by itself. Therefore this way of earning money is greatly in conflict with the natural law.
AristotleThe goodness or badness, justice or injustice, of laws varies of necessity with the constitution of states. This, however, is clear, that the laws must be adapted to the constitutions. But if so, true forms of government will of necessity have just laws, and perverted forms of government will have unjust laws.
Aristotle